<!DOCTYPE html>
<html lang="en">
  <head>
    <meta charset="UTF-8" />
    <meta name="viewport" content="width=device-width, initial-scale=1.0" />
    <title>Document</title>
  </head>
  <body>
    <script>
      function m() {
        let a = prompt("请输入银行卡余额");
        let b = prompt("请输入当月食宿消费余额");
        let c = prompt("请输入生活余额");
        return a - b - c;
      }
      let mm = m();
      document.write(`当前余额剩余${mm}元`);
    </script>
  </body>
</html>
